Westminster is on lockdown this afternoon after a “terror attack” left a female pedestrian dead and at least a dozen people hurt – including some with “catastrophic” injuries – outside the Houses of Parliament.

Gunfire was heard just before 3pm in central London, with a government minister confirming a police officer was stabbed and the assailant shot by armed police.

There are reports of further violent incidents nearby, and police say they have been called to a firearms incident on nearby Westminster Bridge.

Witnesses said a vehicle struck several people on the bridge, and photos showed a car plowed into railings.

Scotland Yard said the attack in Westminster was being treated “as a terrorist incident until we know otherwise”.

The Metropolitan Police added in a statement that the incident is ongoing and are urging people to stay away from the area.

The Parliament complex is now on lockdown. Deputy Commons Speaker Lindsay Hoyle told MPs they would be the last parliamentary staff to be evacuated, and would be moved out in groups of 20.

I am locked in my office with other MPs and frightened young researchers. We have broken open a bottle of whiskey.

It is not known where May was taken or where she currently is although a Downing Street spokesman confirmed she will chair a meeting of the Government’s emergency Cobra committee later today.

Journalists based at Westminster reported they began being evacuated from the Press Gallery just before 5pm

A separate eyewitness who was in Parliament at the time told HuffPost UK: “I heard what sounded like an explosion and raised voices outside Parliament, and so I rushed to the window.

“I saw people running past the entrance to the New Palace Yard entrance to Parliament, and then at least one person try to run into the Yard itself. A police officer chased this person and wrestled them to ground.

“Shots were then fired, but I can’t remember how many and I didn’t see who fired them.

“I ran down the stairs from my office overlooking the Yard to get more information, but the police prevented us from leaving the stairwell.

“When I returned to my office, I could see two people lying on the ground outside Westminster Hall, but neither of these were the person I saw wrestled down by the police officer minutes earlier.”

A junior doctor at nearby St Thomas’ Hospital, Colleen Anderson, described a scene of carnage as people fled the attacker.

She said: “There were people across the bridge. There were some with minor injuries, some catastrophic. Some had injuries they could walk away from or who have life-changing injuries.”

Other political reporters based in the area shared their version of events:

Emergency services trying to revive an individual lying on pavement some way away from entrance to parliament on Parliament Street. pic.twitter.com/bmytpXZ11p